/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cocoon.woody.expression;
import org.outerj.expression.AbstractExpression;
import org.outerj.expression.Expression;
import org.outerj.expression.ExpressionContext;
import org.outerj.expression.ExpressionException;
/**
* Returns true if argument is null.
*
* @author <a href="mailto:vadim.gritsenko@dc.gov">Vadim Gritsenko</a>
* @version CVS $Id: IsNullFunction.java,v 1.5 2004/03/09 13:54:24 reinhard Exp $
*/
public class IsNullFunction extends AbstractExpression {
public Object evaluate(ExpressionContext context) throws ExpressionException {
Object result = null;
try {
result = ((Expression)arguments.get(0)).evaluate(context);
} catch (ExpressionException e) {
// FIXME: Hack to handle null variables
if (!e.getMessage().startsWith("Unknown variable")) {
throw e;
}
}
return result == null? Boolean.TRUE: Boolean.FALSE;
}
public void check() throws ExpressionException {
if (arguments.size() != 1) {
throw new ExpressionException(getDescription() + " requires one argument.", getLine(), getColumn());
}
}
public Class getResultType() {
return Boolean.class;
}
public String getDescription() {
return "IsNull function";
}
}